Efficient 2D Optical Beamforming Network With Sub Partitioning Capability Based on Raised Cosine Chirped Fiber Grating and Mach-Zehnder Delay Interferometer

In this paper, a two-dimensional true time delay optical beamforming network (OBFN) has been proposed with sub partitioning capability for 3X3 phased array antenna (PAA) with operating frequency in X-Band. The architecture is based on raised cosine apodised chirp fiber Bragg grating (CFBG) and Mach-Zehnder delay interferometer (MZDI). Compared to unapodised CFBG, raised cosine apodization drastically reduces the ripple as well as sidelobes and gives a flat response in the passband of reflection spectrum. Multiwavelength optical signals with a wavelength difference of 0.3 nm are used to steer 10 GHz RF signal in elevation and azimuth direction. Further, broad angular control of beam radiation due to sub partitioned PAA is also demonstrated. The RF signal beam is steered in elevation at -62.2,-31.9, and-10.8 degrees, and in azimuth at 123.6 and 55.9 degrees. Theoretical analysis of the OBFN has been presented and validated with the experimental results. At the best of our knowledge, delay characteristics of raised cosine apodised CFBG have been theoretically explored for the first time with mathematical formulation and a comparative discussion is given with the measured data.